Basic Qualification · B-003 Station assembly, practice and safety · B-003-011-005
In what emission mode does the instantaneous amplitude (envelope) of the RF signal vary with the modulating audio?
- A Frequency modulation
- B Pulse modulation
- C Frequency shift keying
- D Amplitude modulation
Correct answer: D — Amplitude modulation. From the official ISED question bank, verified word for word.
Why
Amplitude modulation is the correct choice because the term "amplitude" refers to the strength or height of the radio wave, and this method changes that strength to match the audio signal, creating a visible envelope that rises and falls with the voice. The full explanation — and one for every question — is in Pro.
Practise this section
Building a station safely: power supplies, grounding, RF exposure, lightning, feedline routing, and what a transmitter, receiver and transceiver actually do.